German Patent Application No. 42 18 647 describes a conventional high-voltage discharge lamp device in which the output voltage of the step-up d.c.-d.c. converter of the high-voltage discharge lamp is supplied with alternating polarities. Thus the voltage applied to the gas discharge lamp alternates in a square wave between positive and negative output voltage values of the d.c.-d.c. converter. At a constant polarity reversal frequency, the resulting average voltage applied to the gas discharge lamp thus corresponds to the reference potential. If the gas discharge lamp is accommodated in a housing which is also at this reference potential, there is no potential difference to suppress harmful migration of ions in the lamp.
To create a potential difference between the gas discharge lamp and the environment, German Patent No. 41 41 804 provides a part which is set to a positive potential in comparison with the gas discharge lamp. However, this arrangement involves an additional manufacturing expense.